allow multiple selection lists in a shutdown simulation

I am currently working on a long-term planning of our pipeline renovation projects. I need to determine which projects can be executed simultaneously. My approach at this time is to create a selection list of all the pipes that would be taken out of order for the different projects I would like to combine. Each new combination of projects requires me to create a new selection list and reselect all the pipes affected by these projects. It would be easier for me if I could create separate selection lists for the affected pipes for each individual project, and then select multiple selection lists when running a shutdown simulation for a combination of projects. This would save me a lot of time.